Waveguide for simultaneously transmitting two electromagnetic waves

ABSTRACT

A flexible waveguide for the simultaneous transmission of two perpendicularly disposed linearly polarized electromagnetic waves. The waveguide is in the form of a hollow, elongated, thinwalled flexible metal body which has a constant cross-sectional profile along its longitudinal axis. The outer periphery of the cross-sectional profile is approximately quadratic with rounded corners and constitutes a continuous smooth curve free of abrupt changes in slope. The inner periphery of the cross-sectional profile defines the cross section of a longitudinally extending recess. The cross section of the recess is in the form of two, overlapping, identical ellipses having major axes which are perpendicular to one another.

11 3,79,905 [451 Feb. 5, 1974 1 1 WAVEGUIDE FOR SIMULTANEOUSLYTRANSMITTING TWO ELECTROMAGNETIC WAVES [75] Inventor: ErichSchiittliiffel, Backnang,

Germany [73] Assignee: Licentia Patent Verwaltungs-GmbI-l,

. Frankfurt, Germany [22] Filed: Nov. 24, 1971.

[21] Appl. No.: 201,661

[30] Foreign Application Priority Data Dec. 3, 1970 Germany P 20 59494.9

[52] US. Cl. 333/95 A, 333/95 R [51] Int. Cl H01 3/12, HDlp 3/14 [58]Field Of Search 333/95 R, 95 A, 98

[56] References Cited UNITED STATES PATENTS 2,441,574 5/1948 .laynes333/95 R 3,585,540 6/1971 Schuttloffel et al. 3,336,544 8/1967 Krank eta1. 333/95 R 3,404,357 10/1968 Krank et a1. 333/95 R 3,588,760 6/1971Bondon 333/95 A 3,603,905 9/1971 Schuttlolfel 333/95 R 3,659,234 4/1972Schuttloffel et a1 333/95 R OTHER PUBLICATIONS Chu, L. J ElectromagneticWaves in Elliptic Hollow Pipes of Metal, Jr. of Applied Physics, 9-1938,pp. 583-591.

Primary Examiner-Rudolph V. Roli nec Assistant ExaminerWm. H. PunterAttorney, Agent, or Firm-George H. Spencer et a1.

[ 5 7] ABSTRACT A flexible waveguide for the simultaneous transmissionof two perpendicularly disposed linearly polarized electromagneticwaves. The waveguide is in the form of a hollow, elongated, thin-walledflexible metal body which has a constant cross-sectional profile alongits longitudinal axis. The outer periphery of the crosssectional profileis approximately quadratic with rounded comers and constitutes acontinuous smooth curve free of abrupt changes in slope. The innerperiphery of the cross-sectional profile defines the cross section of alongitudinally extending recess. The cross section of the recess is inthe form of two, overlapping, identical ellipses having major axes whichare perpendicular to one another.

8 Claims, 2 Drawing Figures WAVEGUIDE FOR SIMULTANEOUSLY TRANSMITTINGTWO ELECTROMAGNETIC WAVES BACKGROUND OF THE INVENTION This inventionrelates to a flexible waveguide for the simultaneous low-attenuationtransmission of two linearly polarized electromagnetic waves. Thepresent invention, more particularly, relates to a flexible, thinwalledwaveguide for the simultaneous low-attenuation transmission of twolinearly polarized electromagnetic waves in which the waves aretransmitted through respective recesses of elliptical cross section.

The increasing demand for communications connections makes it necessaryto utilize available directional antennas in multiple ways. In thisregard it is known to transmit simultaneously two different datacarrying electromagnetic waves over the antenna of a directional radiostation, two distinct, perpendicularly polarized waves being used. Tofeed an antenna which is operated in such a manner two separatedwaveguide arrangements are normally required which are combined at theantenna via a suitable switching device operative for coupling theelectromagnetic waves to the antenna.

It is also possible to transmit simultaneously two distinct,perpendicularly polarized electromagnetic waves through a circularwaveguide.

Circular waveguide techniques and the principle of using dual powerlines, however, are expensive, the former because of the requiredstraight installation and the latter because of the need of using twoseparate waveguide arrangements with their associated switching device.

In a conventional waveguide with a quadratic cross section it ispossible to transmit simultaneously two perpendicular polarizedelectromagnetic waves. The cost of such a waveguide feeder arrangementis still relatively high since a plurality of angle bends in thewaveguide are required which are connected with the straight waveguideportions of the arrangement by means of flange connections. Thisproduces undesirable reflection points. Moreover, this results in asignificant electrical drawback for such a waveguide arrangement has ahigh attenuation when it is nonambiguous. Moreover, in a conventionalquadratic waveguide for the simultaneous transmission of twoperpendicularly polarized electromagnetic waves sufficient decoupling ofthe two polarizations can be attained only in that the quadratic crosssection is produced or maintained, respectively, with the utmostprecision. The same applies to conventional circular waveguidearrangements.

SUMMARY OF THE INVENTION It is the object of the present invention toprovide a flexible waveguide in which the above-described drawbacks areovercome.

This object, as well as others which will become apparent from the textbelow, is accomplished according to the present invention by providing awaveguide in the form of an elongated, hollow, thin-walled, flexiblemetal body having a constant cross-sectional profile along itslongitudinal axis. The outer periphery of the cross-sectional profile isapproximately quadratic with rounded corners and constitutes acontinuous smooth curve free of abrupt changes in slope. The innerperiphcry of the cross-sectional profile defines the cross section of alongitudinally extending recess. The cross section of the recess is inthe form of two, overlapping, identical ellipses having major axes whichare perpendicular to one another.

The flexible metal tube may be made of aluminum.

The flexible metal body is preferably made of a relatively thin metaltube. The thin metal tube is preferably seamless and may be fabricatedby conventional drawing techniques.

The identical ellipses whose major axes are perpendicular to one anotherpreferably, simultaneously form the diagonals with respect to the outerquadratic crosssectional periphery of the flexible metal body.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an end view of a firstembodiment of a flexible waveguide according to the present invention.

FIG. 2 is an end view of a second embodiment of a flexible waveguideaccording to the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention, in theillustrated embodiment of FIG. 1 is in the form of an elongated, hollowmetal body having a thin wall W. The outer periphery Ba of the constantcross-sectional profile of the metal body forms approximately aquadratic structure, or i.e. square having four rounded corners C. Theouter periphery Ba, therefore constitutes a continuous smooth curvesince it is free of any abrupt changes or bends along its path. Theinner periphery Bi of the crosssectional profile of the waveguide isdefined by two overlappingellipses E1 and E2 which both have the samecenter point M. The elipses El and E2 are identical and are rotationallydisplaced by about with respect to one another so that the inner recessof the waveguide corresponds approximately to the shape of a four-petalrosette. The major axis of the ellipse E1 is designated DI; the majoraxis of the ellipse E2 is desig nated D2. The two above-mentioned majoraxes D1 and D2 coincide with the diagonals of the approximate squarewhich constitutes the outerperiphery Ba of the metal body. The minoraxis of ellipse Ell is designated dl. The minor axis of the ellipse E2corresponds in length to the minor axis d1 and is designated d2.

The dimensions of the two ellipses El and E2 forming the inner crosssection are such that the ratios of each of the minor axes d1 and d2 tothe respective major axes D1 and D2 lie in a range between 0.55 and 0.85and preferably are 0.65. The thickness of the thin waveguide wall W isso selected that the waveguide is characterized by sufficientflexibility with simultaneously sufficient rigidity in dependence on thematerial constants.

Preferably, the waveguide of the present invention, illustrated in FIG.I, is produced in the form of a seamlessly drawn aluminum tube. As shownin FIG. 1, the thickness b3 of the waveguide wall in the vicinity of therounded comers C of the outer periphery Ba of the cross-sectionalprofile,i.e., in the vicinity of the major axes D1 and D2 of the twoellipses, is about 2 millimeters. In the vicinity of the intersectionsof the two ellipses E1 and E2, the wall thickness b1 is selected to beabout 4 millimeters, while the wall thickness b2 in the space midwaybetween the corners C of the outer pe- 3 riphery Ba of the quadraticcross-sectional profile and the intersections of the ellipses El and E2is approximately 1 millimeter.

The present invention, in the illustrated embodiment shown in FIG. 2 isin the form of an elongated, hollow metal body having a thin wall W. Theouter periphery Ba of the cross-sectional profile of the metal bodyagain forms approximately a square having four rounded corners C. Theouter periphery Ba constitutes a continuous smooth curve free of abruptchanges in slope; The inner periphery Bi of the crosssectional profileof the waveguide is defined by two overlapping ellipses E1 and E2 whichboth have the same center point M. The ellipses El and E2 are identicaland are rotationally displaced by about 90 with respect to one anotherso that the inner recess of the waveguide corresponds approximately tothe shape of a four-petal rosette. The major axis of the ellipse E1 isdesignated D1; the major axis of ellipse E2 is designated D2. The twoabove-mentioned major axes D1 and D2 coincide with the diagonals of theapproximated square which constitutes the outer periphery Ba. The minoraxes of the ellipses E1 and E2 are respectively designated d1 and d2.

The dimensions of the two ellipses E1 and E2 forming the inner crosssection are such that the ratios of each of the minor axes d1 and d2 tothe respective major axes D1 and D2 lie between 0.55 and 0.85 andpreferably are 0.65. The thickness of the waveguide wall W is soselected that the waveguide receives sufficient flexibility withsimultaneously sufficient rigidity in dependence on the materialconstants.

In the preferred embodiment of the present invention shown in FIG. 2,the outer, approximately square crosssectional profile Ba is so designedthat the surfaces between the rounded corners C are symmetricallyoutwardly curved.

Preferably, the waveguide of the present invention, as shown in FIG. 2,is produced in the form of a seamlessly drawn aluminum tube. Thethickness b3 of the waveguide wall in the area of the rounded corners Cof the outer periphery Ba of the cross-sectional profile, i.e. in thevicinity of the major axes D1 and D2 of the two ellipses, is about 1millimeter. In the vicinity of the intersections of the two ellipses Eland E2, the wall thickness bl is selected to be about 5 millimeters,while the wall thickness b2 in the space midway between the corners C'of the outer approximately quadratic periphery Ba and the intersectionsof the elliptinuous fabrication process. The waveguide permits thesimultaneous transmission of two perpendicular waves in such a mannerthat in spite of bending and/or twisting of the waveguide there ismaximum mutual decoupling. The previously required switching devices asthey were discussed in the introduction to this specification are thuseliminated.

It will be understood that the above description of the presentinvention is susceptible to various modifications, changes andadaptations, and the same are intended to be comprehended within themeaning and range of equivalents of the appended claims.

I claim:

1. A flexible waveguide for the simultaneous transmission of twoperpendicularly disposed linearly polarized electro-magnetic wavescomprising an elongated, hollow, thin-walled, flexible metal body havinga substantially constant cross-sectional profile along its longitudinalaxis, the outer periphery of said crosssectional profile beingapproximately quadratic with rounded corners and constituting acontinuous smooth curve, free of abrupt changes in slope; and the innerperiphery of said cross-sectional profile defining the cross-section ofa longitudinally extending recess, in the form of two, overlapping,identical ellipses having their major axes perpendicular to one another.

2. A flexible waveguide as defined in claim 1 wherein said major axescoincide with the diagonals of said outer periphery of saidcrosssectional profile.

3. A flexible waveguide as defined in claim 2 wherein said flexiblemetal body comprises a seamless metal tube.

4. A flexible waveguide as defined in claim 1 wherein the ratio of theminor axis to the major axis of each ellipse is in a range fromsubstantially 0.55 to substantially 0.85.

5. A flexible waveguide as defined in claim 4 wherein said ratio issubstantially 0.65.

6. A flexible waveguide as defined in claim 1 wherein said outerperiphery of said cross-sectional profile between said corners issymmetrically outwardly curved.

7. A flexible waveguide as defined in claim 1 wherein the thickness ofthe wall of said flexible metal body in the vicinity of said corners isapproximately 2 millimeters, in the vicinity of the intersections of thetwo ellipses is approximately 4 millimeters and in the spacesubstantially midway between said corners and said intersections isapproximately 1 millimeter.

8. A flexible waveguide as defined in claim 3 wherein said flexiblemetal body comprises a seamless, drawn,

aluminum tube.

1. A flexible waveguide for the simultaneous transmission of twoperpendicularly disposed linearly poLarized electro-magnetic wavescomprising an elongated, hollow, thin-walled, flexible metal body havinga substantially constant cross-sectional profile along its longitudinalaxis, the outer periphery of said cross-sectional profile beingapproximately quadratic with rounded corners and constituting acontinuous smooth curve, free of abrupt changes in slope; and the innerperiphery of said cross-sectional profile defining the cross-section ofa longitudinally extending recess, in the form of two, overlapping,identical ellipses having their major axes perpendicular to one another.2. A flexible waveguide as defined in claim 1 wherein said major axescoincide with the diagonals of said outer periphery of saidcross-sectional profile.
 3. A flexible waveguide as defined in claim 2wherein said flexible metal body comprises a seamless metal tube.
 4. Aflexible waveguide as defined in claim 1 wherein the ratio of the minoraxis to the major axis of each ellipse is in a range from substantially0.55 to substantially 0.85.
 5. A flexible waveguide as defined in claim4 wherein said ratio is substantially 0.65.
 6. A flexible waveguide asdefined in claim 1 wherein said outer periphery of said cross-sectionalprofile between said corners is symmetrically outwardly curved.
 7. Aflexible waveguide as defined in claim 1 wherein the thickness of thewall of said flexible metal body in the vicinity of said corners isapproximately 2 millimeters, in the vicinity of the intersections of thetwo ellipses is approximately 4 millimeters and in the spacesubstantially midway between said corners and said intersections isapproximately 1 millimeter.
 8. A flexible waveguide as defined in claim3 wherein said flexible metal body comprises a seamless, drawn, aluminumtube.